short



0ct. 6, 1959 B. H. SHORT R 24,715

VEHICLE ELECTRICAL SYSTEM Original Filed Jan. 16. 1956 )0 II I jg o M,,3 .1 ii if? -3 1 w: H -24 L 1i I N V EN TOR. BRO0K6 Ii SIM/3 T Re.24,715 Reissued Oct. 6, 1959 United States Patent Oiiice VEHICLEELECTRICAL SYSTEM Brooks H. Short, Anderson, Ind., assignor to GeneralMotors Corporation, Detroit, Mich., a corporation of Delaware OriginalNo. 2,809,301, dated October 8, 1957, Serial No. 559,189, January 1-6,1956. Application for reissue May 1, 1959, Serial No. 810,518

8 Claims. Cl. 290-40 Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention relates to electrical systems for motor vehicles and ismore particularly concerned with certain improvements in batterycharging systems of the type wherein the battery which is connected witha D.C. load circuit is charged by a dynamoelectric unit whose speedvaries greatly and which is driven by the prime mover of the motorvehicle.

The advantages of a battery charging system in a motor vehicle whichincludes an alternator as a source of charging current and voltage arewidely accepted for, when an alternator is used, a considerably higheroutput current and voltage can be obtained when the vehicle is operatedat idling speeds. These systems usually are provided with a rectifierwhich changes the alternating output current of the alternator to directcurrent to supply the various electrical devices in the motor vehiclewith D.C. current and to charge the storage battery. Also included inthese systems are a plurality of mechanical relays which are arranged tomaintain the output of the alternator substantially constant regardlessof the speed of the vehicle engine and to prevent the discharge of thebattery through the alternator circuit network when the vehicle engineis at rest.

One of the objects of ,the present invention is to provide a batterycharging system in a motor vehicle in which a considerably increasedoutput of electrical energy is obtained for lower engine speeds than hasheretofore been possible and to control this output with a device whichhas no mechanical moving parts such as relays which are normally used tocontrol the charging of the battery charging circuit.

It is another object, therefore, of the present invention to provide analternating current battery charging system in a motor vehicle with asilicon power rectifier which changes the alternating current output ofthe alternator to direct current for battery charging and other purposesand prevents the fiow of current from the battery through saidalternator when the vehicle engine is at rest.

A further object of the present invention is to provide a regulatingsystem for an alternator wherein a transistor is used to control theenergization of the alternator field windings in response to the outputof a silicon rectifier which changes the output of the alternator fromA.C. to D.C. current for battery charging and other purposes andprevents the discharge of said battery through said alternator duringperiods when the vehicle engine which drives the alternator is at rest.

A still further object of the present invention is to eliminate the useof a cutout relay in a battery charging system that includes analternator whose output is controlled by a transistor voltage regulatorby utilizing the blocking effect of a silicon rectifier to eliminate theflow of current from the battery to the alternator when the alternatoris at rest.

Further objects and advantages of the present inventrical output atidling speeds.

erence being had to the accompanying drawing wherein a preferredembodiment of the present invention is clearly shown.

In the drawings:

The single figure shown diagrammatically illustrates a Wiring diagram ofa motor vehicle battery charging systern according to the presentinvention.

In the present day battery charging systems as used in motor vehicles, adirect current generator is usually employed to supply the necessarycurrent and voltage for battery charging and other electrical loads.These direct current generators have their fields controlled byvibrating relays which are circuited to vary the energization of thefield to maintain the generator output substantially constant and withinlimits which will not prove harmful to the electrical components of thesystem or to the battery. While systems of this type have enjoyedcommercial acceptance, certain objectionable characteristics have beennoted as when the contacts of the control relays become welded togetheror the calibration of the relays is upset to cause injuryto the batteryor generator. These systems have further been found objectionable undercertain conditions because of their inherent low elec- To overcome thelatter objection, it has been proposed to replace the direct currentgenerator with an alternator. In commercial systems of this type, theoutput of the alternator is generally rectified to direct current by arectifier and the output of the rectifier, in turn, is connected througha cutout relay with the battery. The cutout relay, in turn, is controlled by an external means arranged so the relay will be closed onlywhen the alternator is being rotated sulficiently to provide a batterycharging current. If this arrangement is not used, it has been foundthat during periods when the circuit between the rectifier and batteryis opened and the output of the alternator is still relatively high, thehigh transient voltages which are set up by the rapid collapse of thealternator field will cause severe injury to the rectifier.

The present invention is directed to a battery charging system whereinthe above objectionable features have been eliminated. This isaccomplished by changing the output of the alternator in a siliconrectifier and controlling this output by a transistor network circuit.This arrangement will eliminate all of the relays which have beenheretofore used and will utilize the blocking effect of the siliconrectifier to prevent discharge of the battery during periods when themotor vehicle is idle for an appreciable length of time.

The use of a silicon rectifier in the above system possessesconsiderable advantages over other rectifiers as heretofore employed asit has been found that the silicon rectifier has only a .4 to 1 voltdrop when the rectifier is conducting in the forward direction against a2.4 volts dropwhen other rectifiers, i.e., a selenium rectifier is used.Further, in the reverse direction, the silicon rectifier will withstandabout ten times the voltage across its terminal as will the seleniumrectifier. These advantages together with the fact that the siliconrectifier will be conductive in the microamp range in the reversedirection whereas the other type of rectifiers such as the seleniumrectifiers heretofore used are conductive in the high milliamp rangemakes possible the use of a single rectifier in the type of batterycharging system herein contemplated so as to eliminate the requirementfor a mechanical relay and additional rectifiers which have beenheretofore employed.

In the drawing, the alternator or A.C. generator 10, which is shown, maybe of any suitable conventional types such as a Y or delta connectedunit Which is suitable for use in motor vehicles. The alternator 10 isprovided with output terminals 11 which are connected through leads 12with the input terminals 13 of the silicon rectifier 14. The outputterminals 15 of the rectifier 14 are connected through leads 24 and 26to the battery 16 and to other electrical loads, not shown. Thealternator has its field 17 controlled by a means which will behereinafter described and which are similar to the control set forth inapplication, S.N. 546,503, filed November 14, 1955, which has beenassigned by the inventors to the 'assignee of the present invention.

In'the drawing, it will be seen that the variable resistance 32 isconnected between the output terminal of the rectifier 14 and thebattery 16. The field winding 17 of the alternator 10 has one endconnected directly to lead 26 and the opposite end connected through asuitable switch 18 to the collector electrode 31 of transistor 30. Theswitch 18 maybe the ignition switch of the prime mover if desired. Theemitter electrode 40 of transistor 30 is connected to lead 24 which, inturn, is connected to the positive output terminals 15 of the siliconrectifier 14. The base 42 of transistor 30 is connected directly througha lead 44 to the emitter electrode 46 of a transistor 48. A resistance50 is connected between leads 44 and 24. The collector electrode 52 oftransistor 48 is connected through a resistance 54 with lead 26 and thebase 56 of transistor 48 is connected through a lead 58 with a collectorelectrode 60 of a transistor 62. The lead 58 has one end connectedthrough a resistance 64 to lead 26 and the other end connected through aresistance 66'with lead '24. The emitter electrode 68 of transistor 62is connected directly to lead 24 and the base 70 is connected through alead 72, a rectifying diode 74 and a lead 76 to a variable tap 7 8 on avariable resistance 34. A resistance 80 is connected between the lead 72and lead 24 and a second rectifying diode 82 is connected between ajunction 84 and lead 72. The variable resistance 34 has one endconnccted through a resistance 86 with lead 26 and the other endconnected through a resistance 88 with lead 24 on the battery side ofresistance 32. The emitter electrode 90 of the transistor 92 is directlyconnected to lead 24 and the collector electrode 94 of transistor "92 isconnected with junction 84. The base96 of the transistor 92 is connectedthrough a junction 98 with the collector electrode 100 of a transistor102. The resistances 1 04 and 106 each have one end respectivelyconnected with junctions 84 and 98 andthe other ends connected with lead26. The transistor 102 has its emitter electrode 108 connected to therectifier 14 side of the variable resistance 32 and the base 110connected to the battery 16side of the variable resistance 32. Thecondenser 112 is connected between leads 76 and 24 and is includedtorender the regulator means responsive to theaverage direct currentoutput of the rectifier.

The diode rectifiers 74 and 82 are of the type known as Zener diodeswhich breakdown upon the application of a higher voltage than that forwhich they are designed so that current may flow-through them in thereverse direction when the voltage exceeds a predetermined value.However, upon restoring the normal voltage or less thereacross theyrecover their rectifying or blocking action without damage.

In operation, the current and voltage regulating system will function asfollows to control the flow of current through the field 17 to thealternator 10. When the alternator 10 is producing an A.C. outputcurrent and voltage through the rectifier 14 sufficient to charge thebattery 16, current will flow through the resistance 32. When currentflows through resistance 32, the base of the transistor 102 will becomenegative with respect to the emitter and cause the current throughresistance 106 to be shifted from the base circuit of transistor 92tothe collector circuit of transistor 102. As this shift occurs, thebase current in transistor 92 is reduced. Since the collector current ina transistor is a function of the base current, and as the base currentin transistor 92 is decreased; it

therefore follows that the collector current in transistor 92 will bedecreased and the current from collector of transistor 92 throughresistance 104 is decreased. This means that as the current in theresistance 32 is increased, the current in resistance 104 is decreased.Such a decrease in current in resistance 104 results in a lower voltagedrop in the resistance 104 thereby moving the potential of junction 84closer to the negative side with an increase in current in resistance32.

When the potential between lead 24 and junction 84 exceeds the Zenercurve value of the diode '82, the diode 82 will permit current to passthrough the resistance to cause the base 70 of transistor 62 to becomeconductive. When the transistor 62 is conductive, it will control theaction of transistors 30 and 48, as will be hereinafter described, tovary the current flow through field 17 to regulate the output ofalternator 10 in response to the current flowing through the variableresistance 32.

The control of the base current of transistor 62 is determined by theHow of current through the Zener diodes 82 or 74. When these diodes 82or 74 are non-conductive, no current will pass through the base circuitof transistor 62. The Zener diode 82 is rendered conductive in responseto current flow through resistance 32 as heretofore set forth. When thevoltage output of alternator 10 exceeds a predetermined value, asdetermined by the setting of tap 78, the potential imposed across Zenerdiode 74 will exceed its Zener curve value and diode 74 will beconductive. The setting of tap 78 on resistance 34 will determine theconductivity of diode 74. The greater the value of the resistance 34, asis determined by the location of tap 78, that is added to resistance 88,then the greater is the percentage of the voltage between leads .24 and26 that will be imposed across diode 74, so when a predetermined voltageis impressed across diode 74, a lower in the voltage device, athree-stage transistor amplifier is desirable. By using the circuitshown, the transistors 30 and 48 work in the same direction and do notreverse the phase. When the Zener diode 74 or 82 is made conductive, thebase circuit of transistor 62 will be made conductive and the-collectorcircuit; of transistor 62 will pass current through resistance 64. Thiswill cause the base current in transistor 48 to decrease. The current inthe collector of transistor 48 is equal to beta times the change in thebase current. Thus, the current flowing through the emitter oftransistor 48 is equal to (beta plus 1) times the change in the basecurrent of transistor 48 which will fiow'through either resistance 50 orthrough which is the collector current. oftransistor 30, is greatlyreduced.

From the above, it is apparent that the variable resistance 32, thetransistors 102, 92, the current limiting resistances 104 and 106 andthe Zener diode 82 are used to control the energization of the fieldthrough the transistor network which includes transistor 30 in responseto the current which flows through the resistance 32.

A rectifier 19 is placed in parallel with the field 17 to absorbtransients that may otherwise damage the transistor 30.

While the embodiment of the present invention 'as herein disclosed,constitutes a preferred form, it is to e derstood that other forms mightbe adopted.

What is claimed is as follows:

1. In an electrical system for a motor 'vehicle having a variable speeddriving engine and a direct current load including a storage battery,the combination comprising; an alternator having load terminals and anexciting field Winding, torque transmitting means connecting saidalternator with said driving engine to be driven thereby, a siliconrectifier having input terminals connected with the load terminals ofsaid alternator and output terminals connected with said direct currentload, and a transistor regulating means connected in circuit with saidexciting field winding and the output terminals of said rectifier andoperable by the rectified voltage of said rectifier for regulating theexcitation of said field windmg.

2. In an electrical system for a motor vehicle having a variable speeddriving engine and a D.C. load including a storage battery, thecombination comprising; an alternator having load terminals and anexciting field arranged to vary the current and voltage output of saidalternator, a silicon rectifier having input terminals connected to saidload terminals and output terminals connected with said D.C. load forsupplying D.C. voltage and current to said D.C. load whenever thevoltage output of said alternator exceeds the potential of said battery,and a means connected to the output terminals of said rectifier andfield for varying current in said field in response to variations involtage at the output terminals of said rectifier, said means. includinga transistor and -a means connected in circuit with said transistor andoutput terminals of said rectifier.

3. In a motor vehicle having a variable speed driving engine, anelectrical system comprising in combination; an alternator driven bysaid engine and having an exciting field winding and load terminals, aD.C. load including a storage battery, a silicon power rectifier havinginput load terminals connected in circuit with the output terminals ofsaid alternator and output terminals directly connected with the D.C.load for supplying rectified current from said alternator directly tosaid battery whenever the voltage acnoss said output terminals exceedsthe voltage of said battery, and a transistor means connected betweenthe output terminals of said rectifier and said field winding forvarying the excitation of said field in response to the potential ofsaid output terminals.

4. In a motor vehicle having a variable speed driving engine, anelectrical system comprising in combination; an alternator driven bysaid engine and having an exciting field winding and load terminals, aD.C. load including a storage battery, a silicon power rectifier havinginput load terminals connected in circuit with the output terminals ofsaid alternator and output terminals directly connected with the D.C.load for supplying rectified current from said alternator directly tosaid battery when ever the voltage across said output terminals exceedsthe voltage of said battery, and a means including a transistor networkconnected between the output terminals of said rectifier and said fieldwinding for selectively varying the excitation of said field in responseto the current flow and the potential present at said output terminals.

5. In a motor vehicle having a variable speed driving engine, anelectrical system comprising in combination; an alternator driven bysaid engine and having an exciting field winding and load terminals, aD.C. load including a storage battery, a silicon power rectifier havinginput load terminals connected in circuit with the output terminals ofsaid alternator and output terminals directly connected with the D.C.load for supplying rectified current from said alternator directly tosaid battery whenever the voltage across said output terminals exceedsthe voltage of said battery, and a means including a Zener diode and atransistor connected between the output terminals of said rectifier andsaid field winding for varying the excitation of said field in responseto the potential of said output terminals.

6. In a motor vehicle having a variable speed driving engine, anelectrical system comprising in combination; an alternator driven bysaid engine and having an exciting field winding and load terminals, aD.C. load including a storage battery, a silicon power rectifier havinginput load terminals connected in circuit with the output terminals ofsaid alternator and output terminals directly connected with the D.C.load for supplying rectified current from said alternator directly tosaid battery whenever the voltage across said output terminals exceedsthe voltage of said battery, and transistor means connected to theoutput terminals of said silicon rectifier and to said field to controlthe flow of current through the field in response to the voltage acrosssaid output terminals.

7. In an electrical system for a motor vehicle having a direct currentload circuit including a storage battery, a variable source of electriccurrent and voltage connected in circuit with said D.C. load forsupplying current and voltage to said load and charging said batterywhen the voltage at said source exceeds the battery voltage, a siliconrectifier connected in said circuit between said source and battery forpreventing the flow of current from said battery to said source and aregulating means including a transistor having a base and emitterconnected to said circuit between said silicon rectifier and battery anda collector connected in circuit with said source for maintaining thevoltage of said source substantially constant.

8. In an electrical system for a motor vehicle having a direct currentload circuit including a storage battery, a variable source of electriccurrent and voltage connected in circuit with said D.C. load forsupplying current and voltage to said load and charging said batterywhen the voltage at said source exceeds the battery voltage, a pnjunction semiconductor rectifier connected in said circuit between saidsource and battery for preventing the flow of current from said batteryto said source and a regulating means including a transistor having abase and emitter connected to said circuit between said rectifier andbattery and a collector connected in circuit with said source formaintaining the voltage of said source substantially constant.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 2,117,141 Breer et al. May 10, 1938 2,494,749Fagen et a1. Jan. 17, 1950 2,557,298 Leece et al. June 19, 19512,558,644 Claytor June 26, 1951 2,740,086 Evans et a1. Mar. 27, 19562,751,549 Chase June 19, 1956 2,751,550 Chase June 19, 1956 2,759,142Hamilton Aug. 14, 1956

